(i) Field of the Invention
The present invention relates to a colored curable composition constituting a color filter used for liquid crystal display elements and solid state image pick-up elements and suitable for forming colored images, as well as to a color filter using the colored curable composition and a process of preparing the color filter.
(ii) Description of the Related Art
As processes for preparing a color filter used for liquid crystal display elements and solid state image pick-up elements, a staining process, a printing process, an electrodeposition process and a pigment dispersion process are known.
In the pigment dispersion process, the color filter is prepared by a photolithographic process using a colored radiation-sensitive composition prepared by dispersing a pigment in a photosensitive composition. A sufficient degree of positional accuracy can be obtained in this process since the pigment is patterned by the photolithographic process, and this process has been widely used as a process suitable for preparing the color filter for a large screen and high accuracy color display.
In preparing a color filter by the pigment dispersion process, the radiation-sensitive composition is first coated on a support with a spin coater or roll coater and dried to form a coating film. Then, colored pixels are obtained by patterned-exposure and development of the coating film. The color filter can be prepared by repeating this operation a number of times corresponding to the number of hues.
The above pigment dispersion process proposes use of a negative photosensitive composition using together a photo polymerizable monomer, a photopolymerization initiator, and an alkali-soluble resin (e.g., see, Japanese Patent Application Laid-Open (JP-A) Nos. 2-199403).
Recently there is a need to further increase the high-definition of color filters for solid state image pick-up elements. In conventional pigment dispersion processes, however, it is difficult to enhance the resolution further, and there are problems such as color unevenness due to the coarse particles of pigments. They are not suited to uses demanding fine patterns, such as solid state image pick-up elements.
In the light of such problems, it has been hitherto proposed to use a dye instead of a pigment (e.g., see, JP-A No. 6-75375). Further reductions in layer thickness are desired in color filters for solid state image pick-up elements. In order to satisfy both sufficient coloring concentration and layer thinness, a large amount of coloring agent (dye) needs to be added to the photosensitive composition, with decreases in the content of other materials in the composition. When a dye is used as a coloring agent, tolerance to organic solvents is insufficient. When a subsequent color pattern is coated superposed on a pattern that has already been formed, the problem that the dye in the pattern may elute (referred to as “decoloring”) may occur. In the photosensitive composition, for example, when the amount of an organic solvent soluble dye is increased, and the amount of other materials is decreased, the dye in the pattern that has already formed may elute significantly when a subsequent color pattern is coated (e.g., see, JP-A No. 2004-246106).